Friday, August 10, 2012

Specialized cryptanalytic machines of WWII

Histories of
WWII only tend to devote a few pages on codebreaking and when they do they
usually focus on well known individuals such as William Friedman, Alan Turing,
Gordon Welchman etc

The reason
they do so is that we as humans like to connect a specific event with a face.
For example Purple cipher machine=Friedman, Enigma success=Turing.

It’s
undoubtedly a very simplistic way to view things but that’s what the average
person wants. Of course only rarely can a specific success be traced back to
one and only one person. Even back in WWII whole teams had to work to solve
difficult crypto systems.

One thing
that doesn’t get the attention it deserves is the use of specialized
cryptanalytic devices for ‘breaking’ hard systems. Again I think the problem is
our inherent need to identify humans as protagonists of important events.

Even so
without bombes, duennas, autoscritchers, IBM punch card machines and various
other specialized equipment many Allied codebreaking successes would be
impossible.

Let’s take a
quick look at some of the devices built and their targets.

Type

Date Introduced

Target

Date Introduced

3-rotor bombe

18-Mar-40

Plugboard Enigma

1928

4-rotor bombe

Sep-43

M4 Enigma

Feb-42

Duenna

16-Nov-44

Enigma with UKW-D

1943

Autoscritcher

26-Dec-44

''

Giant

end 1944

''

Heath Robinson

Jun-43

SZ40/42

1940/41

Collosus I

Feb-44

''

Collosus II

Jun-44

''

Notice the
long delay from the time a cipher machine is introduced till the time a cryptanalytic
device is used against it. Building a specialized device took a long time and
of course had the inherent problem that it could only be used against that
specific cipher machine.

Postwar the
Anglo-Americans realized that they needed more flexible equipment. This is
explained briefly by the NSA’s Howard Campaigne [Source: NSA-OH-14-83,
p73]:

We had in the past, before that time,
we had built a special device for every problem. And we'd gotten some very
effective devices. But it always took a long time to build it. We had to
formulate the problem and design the equipment, and get it constructed, and
debugged, and all that had to take place when we ought to be operating. And we
saw that we thought with the flexible computer you can put a program on and get
going right away.

The NSA’s
need for a general purpose cryptanalytic device led them to invest great sums
in developing the first computers postwar.